BPP43_05035 is aBrachyspira pilosicolicell surface adhesin that weakens the integrity of the epithelial barrier during infection

Abstract

AbstractThe anaerobic spirocheteBrachyspiracauses intestinal spirochetosis, characterized by the intimate attachment of bacterial cells to the colonic mucosa, potentially leading to symptoms such as diarrhea, abdominal pain, and weight loss. Despite the clinical significance ofBrachyspirainfections, the mechanism behind the interaction betweenBrachyspiraand the colonic epithelium is not known. In this study, we characterized the molecular mechanism ofB. pilosicoli-epithelium interaction and its impact on the epithelial barrier during infection. Through a proteomics approach, we identified BPP43_05035 as a candidateB. pilosicoliadhesion protein that mediates bacterial attachment to cultured human colonic epithelial cells. The crystal structure of BPP43_05035 revealed a globular lipoprotein with a six-bladed beta-propeller domain. Blocking the native BPP43_05035 onB. pilosicoli, either with a specific antibody or via competitive inhibition, abrogated its binding to epithelial cells. Furthermore, the binding of BPP43_05035 to epithelial cells required surface-exposed hostN-glycans. Proximity labeling and interaction assays revealed that BPP43_05035 bound to tight junctions, thereby increasing the permeability of the epithelial monolayer. Extending our investigation to human patients, we identified a downregulation of tight junction and brush border genes inB. pilosicoli-infected patients carrying detectible levels of epithelium-bound BPP43_05035. Collectively, our findings identify BPP43_05035 as aB. pilosicoliadhesin that weakens the colonic epithelial barrier during infection.